Date: Sun, 16 Mar 1997 17:58:42 -0800 From: Scott Blachowicz <scott@bloke.statsci.com> To: neil@corpex.com (Neil) Cc: freebsd-questions@freebsd.org (Questions Freebsd) Subject: Re: SMTP and Firewalls Message-ID: <m0w6RhC-000QdNC@bloke.statsci.com> In-Reply-To: Your message of "Fri, 14 Mar 1997 23:43:45 %2B0000." <m0w5gdV-00044jC@corpex.com> References: <m0w5gdV-00044jC@corpex.com>
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neil@corpex.com (Neil) wrote:
> We are using FBSD 2.1.5 with IPFW configured for a mail server. Other than
> the obvious port 25 connections, what else must be opened in the firewall to
> allow SMTP 'sending'. At present we get a 'operation timed out' error as the
> server cannot connect ot an external server.
Maybe port 113 (the "auth"/"ident") port? I've worked in a setup where the
systems inside the firewall were NOT setup to provide that service, so the
firewall was set to block them. We would get timeouts trying to get to SOME
systems' SMTP daemons. When we opened up the firewall to allow them through,
the connections went through. Our theory was that the remote system was
getting an immediate connection refused after it was opened up, so everything
proceeded just fine. With the firewall blocking them, it appeared as if the
remote systems' SMTP daemons weren't spitting out their '220' welcome message
banners, and our systems (running smail) were hanging waiting for it.
Or at least, that's how it appeared (we didn't go thru the code or trace
anything to confirm the precise cause). Also, note that this wasn't a 2.1.5
IPFW firewall, but on obtained from a 3rd party (I THINK it's really a special
purpose Linux box). And we were using smail instead of sendmail. But the
info might be useful nonetheless...
Scott Blachowicz Ph: 206/283-8802x240 Mathsoft (Data Analysis Products Div)
1700 Westlake Ave N #500
scott@statsci.com Seattle, WA USA 98109
Scott.Blachowicz@seaslug.org
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